Cloud-radiation interaction as simulated by the

Canadian GEM model compared to ARM

observations

Danahé Paquin-RicardDirector: Colin Jones

Codirector: Paul Vaillancourt

Source:http://www.cs.pitt.edu/

1. Motivation

MacroMicrophysics Environment

Cloud-RadiationInteraction

Surface Radiative Budget

Precipitation

2. GEM-LAM v.3.2.2

Diagnostic variables:

Cloud fractionLWC, IWC

rei, rel

Parameterization:Cloud fraction f(RH)& vertical overlap

Liquid-ice separation& effective radii f(T)

Radiation:Correlated-K

Prognostic variables :T, qv, qc, qs, qr

Shallow convection:Kuo-Transient

Deep convection:Kain-Fritsch

Advection

Microphysics:Sundqvist

3. Simulations

Simulations: 53 vertical levels Horizontal resolution:

0,5° Time step: 30 min Prescribed SSTs & ice

fraction LBCs: ERA40 & ECMWF 7/8 years: 1998-

2004/05Source: Ayrton Zadra & Paul Vaillancourt

Source: http://www.arm.gov

NSA

SGP

4. ObservationsARM (Atmospheric Radiation Measurement Program) SGP (Southern Great Plains) NSA (North Slope of Alaska)

Observations: SWD and LWD LWP and IWV Cloud fraction Precipitation Surface T & p

5. Results

3 hourly-mean (except for precip.: 3 hourly accumulation)

Radiation fluxes: function of cloud fraction Clear-sky: CF<10% Overcast: CF>90% All-sky

LWP & IWV: only when precipitation ≤ 0,25mm/3h

5. Cloud fraction, IWV & LWP

5. Cloud fraction, IWV & LWP

5. Cloud fraction, IWV & LWP

5. SWD vs. IWV: clear sky (≤10 %)

5. SWD vs. IWV: clear sky (≤10 %)

C

Local Time (h)

5. LWD vs. IWV: clear sky (≤10

%)

5. LWD vs. IWV: clear sky (≤10

%)

5. SWD vs. LWP: overcast (≥90%)

5. SWD vs. LWP: overcast (≥90%)

Local Time (h)

5. LWD vs. LWP: overcast (≥90%)

5. LWD vs. LWP: overcast (≥90%)

5. SWD

+ CF underestimated

5. LWD

+ CF underestimated

6. Conclusion

Cloud-radiation interaction can modify surface radiative fluxes by different ways

Verification of individual components is important

Thank you for your Thank you for your attention…attention…

Questions ?Questions ?

6. A feedback example

Drier Surface

Less evaporation

Overestimate nearsurf. Temperature

UnderestimateCloud fraction

OverestimateSWD

UnderestimateIWV

5. Résultats

D

5. LWP